A motor-vehicle door latch normally has a housing, a lock fork on the housing engageable with a door bolt and pivotable between a holding position engaged around the bolt and retaining it on the housing and a freeing position permitting the door bolt to move into and out of the housing, and a release pawl engageable with the fork and displaceable between a latched position retaining the fork in the holding position and an unlatched position unengageable with the fork and permitting the fork to move into the freeing position. An actuating mechanism is movable between an actuated position and an unactuated position and normally has an inside and an outside actuating lever connected to respective door handles. A coupling part is displaceable on the housing between a coupling position connecting the actuating mechanism to the release pawl for displacement of the release pawl into the unlatched position on displacement of the actuating mechanism into the actuated position and a decoupling position for disconnecting the actuating mechanism from the release pawl. Thus in the decoupling position operation of the actuating mechanism does not affect the release pawl. A central locking element is displaceable on the housing between locked and unlocked positions and is connected via a locking mechanism normally also operable by at least an inside locking element with the coupling part for displacing the coupling part into the decoupling position on displacement of the central locking element into the locked position and for displacing the coupling part into the coupling position on displacement of the central locking element into the unlocked position.
In a common system the power actuation is effected by a reversible electric motor. In addition there is of course the possibility of a manual locking and unlocking of the door that is particularly useful if the power fails or the power locking is otherwise not operational. To this end the standard actuation element is a spiral groove in which engages a pin and so that the pin is cammed out and in between the locked and unlocked positions, and an additional crosswise groove connects the ends of the spiral groove to allow this manual actuation.
The central locking system described in EP 0,059,658 of J. P. Noel uses a contact lever for controlling and switching the electrical motor of the latch. This contact lever has a pin riding in the cam and represents a cumbersome and expensive system, since the contact lever also forms the input element for the described manual actuation.